typo/wrong parameter name in text of chapter "problematic posteriors"

[jessekps]

Summary:

wrong parameter name in text of problematic posteriors

Description:

https://mc-stan.org/docs/stan-users-guide/problematic-posteriors.html section: Mitigating the invariances subsection: Pinning parameters sentence: "To solve this problem, one of the difficulty parameters, say $\sigma_1$, must also be constrained"

I think you mean to say: one of the "discrimination" parameters

Current Version:

v2.18.0

[bob-carpenter]

Thanks---we'll fix this.